The conventional locking member, as shown in FIG. 1, is widely applied in hand tools, particularly screwdrivers. FIG. 1 shows two typical examples of using the locking member in screwdrivers.
The first example is shown by A in FIG. 1 wherein the locking member is used for temporarily locking a detachable bit 3 within a first hollow sleeve 2 after the bit 3 is inserted into the first hollow sleeve 2 of the screwdriver. The second example is shown by B wherein the locking member temporarily retains a driver rod (such as first hollow sleeve 2 in the figure) of the tool within a handle 1 after the driver rod is inserted into the handle 1. The figure shows that the handle 1 has secured therein a second hollow sleeve 11 and a locking member provided at B for clamping the first hollow sleeve 2. If the diameter of the openings at both ends of the first hollow sleeve 2 are different, in addition to providing a locking member at A of the first end, another locking member is also provided at C of the second end. Generally speaking, the above-mentioned locking member is formed by fitting a spring member 21, such as the conventional C ring, into an annular groove in the inner surface of the first hollow sleeve 2 to clamp an element inserted into the first hollow sleeve 2. Another way of forming the locking member is to provide a ball in the hollow sleeve, the ball being pressed by a spring to project slightly from the inner surface of the hollow sleeve and clamp the rod object or the waist of the rod object inserted into the hollow sleeve as illustrated by B in FIG. 1. The allowed tolerance for this structure is generally 0.20 mm, but in the process of mass production, the distance the ball projects from the inner surface of the hollow sleeve will be greater than the allowed tolerance. As is well known to those skilled in the art, when the ball projects very slightly from the inner surface of the hollow sleeve, its locking function becomes insignificant; relatively, when the ball projects from the inner surface of the hollow sleeve too much, it will be difficult to insert the rod object into the hollow sleeve, and the ball will easily drop out. Another reason why it is hard to control the tolerance in this kind of structure is because when a hexagonal or quadrilateral steel bar is forged into a bit, the diameter of the steel bar will expand, and the expansion value is hard to control. In other words, the first reason is that the tolerance of the ball projecting from the inner surface of the hollow sleeve is difficult to control, and the second reason is that the diameter of the element such as a bit inserted into the hollow sleeve is hard to control. The second drawback may be eliminated by adopting centerless grinding for correction, but the cost of processing is very expensive.
In U.S. Pat. No. 4,644,831, Yang teaches an adaptor sleeve which includes a U-shaped spring clamp plate disposed in a second bore opening of the hollow sleeve for securing a bit inserted into the hollow sleeve. Yang's invention obviously differs from the conventional technique illustrated in FIG. 1 of the present invention in that the rod object cannot insert through any one of the openings of the hollow sleeve as in the conventional technique. Therefore, Yang's invention cannot be applied to the so-called four-in-one or six-in-one driver as shown in FIG. 1.